birthdays for deleted contacts still in icloud.com calendar
Per top level technical support... If you are going to delete a contact that has an associated birthday, do the following: 1. delete the birthday and save the contact with the birthday deleted. 2. make sure the birtday is no longer showing in the icloud.com calendar. 3. delete the contact entirely.
If you delete the contact without following this process, birthdays for deleted contacts will remain in your icloud.com calendar with no way to remove them.
Engineering has been notified of this issue. No ETA for a scheduled fix at this time.